delete_plugins() $redirect argument unused

[jdgrimes]

The second argument for delete_plugins() ($redirect), has been unused since the function was introduced in [8049]. Apparently it was unnecessarily inherited from its forerunners.

[eiffel666333]

Replying to jdgrimes:

The second argument for delete_plugins() ($redirect), has been unused since the function was introduced in [8049]. Apparently it was unnecessarily inherited from its forerunners.

[SergeyBiryukov]

We should probably deprecate it (like in [27162]), in case we ever need to add another argument here.

[jdgrimes]

Deprecate the $redirect argument

[jdgrimes]

Replying to SergeyBiryukov:

We should probably deprecate it (like in [27162]), in case we ever need to add another argument here.

28111.patch​ deprecates the argument. I included a call to _deprecated_argument() if $redirect is passed, though this wasn't done for [27162].

[SergeyBiryukov]

_deprecated_argument() is probably not necessary here.

28111.2.patch​ also contains some PHPDoc fixes and additions.

[SergeyBiryukov]

In 28256:

Deprecate unused argument of delete_plugins(). Clarify @return value.

props jdgrimes for initial patch.
fixes #28111.